Determination of the intrinsic elastic modulus, hardness and fracture strength of thermally growth oxide by nanoindentation and tensile tests

Abstract

Thermally growth oxide (TGO) is formed between ceramic coat and bond coat during the service of thermal barrier coatings (TBCs). Characterization of the mechanical properties of the TGO layer is important for simulating the stress or predicting the failure of TBCs. Based on nanoindentation and tensile methods, the elastic modulus, hardness and fracture strength of TGO are obtained. Due to the influence of the indentation size effect (ISE), the measured indentation hardness and elastic modulus of TGO decrease with increasing indentation depth. These values are much smaller than those of bulk alumina. By analyzing the ISE, the intrinsic hardness and elastic modulus of TGO are obtained as 13.58 GPa and 326.46 GPa, respectively. The residual stress in TGO with the value of 133.1 MPa is determined by XRD method. Combining the tensile tests with a digital image correlation (DIC) method, the tensile fracture strain and fracture strength of TGO are determined to be 0.25% and 683 MPa, respectively.